High frequency signal transmission structure

ABSTRACT

A connection pad, an insulating film, a ground layer a protective film, first to third wirings and posts S 0 , S 1 , G, D on the wirings are disposed on a semiconductor substrate. In this case, the first wiring transmits a high frequency signal, and a dummy pad portion and dummy post D for restraining attenuation of the high frequency signal are disposed midway in the wiring and not connected to external, circuits. An opening for decreasing a floating capacity is disposed in the ground layer under the posts S 0 , D.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is a Continuation Application of PCT Application No.PCT/JP03/14659, filed Nov. 18, 2003, which was not published under PCTArticle 21(2) in English.

[0002] This application is based upon and claims the benefit of priorityfrom prior Japanese Patent Applications No. 2002-337327, filed Nov. 21,2002; and No. 2002-345420, Nov. 28, 2002, the entire contents of both ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] The present invention relates to a high frequency signaltransmission structure including a high frequency signal wiring fortransmitting high frequency signals.

[0005] 2. Description of the Related Art

[0006] For a semiconductor device constituted of a conventional highfrequency circuit, as disclosed in Jpn. Pat. Unexamined Publication No.2002-124593, a device has been known in which a dielectric substrate isdisposed between a semiconductor integrated circuit device of Si, GaAs,or the like, and a circuit substrate. A ground device of thesemiconductor integrated circuit device is connected to a ground line ofthe circuit substrate via a via-hole disposed in the dielectricsubstrate. For the semiconductor device, a built-in integrated circuitis divided and formed in a plurality of circuit blocks in thesemiconductor integrated circuit device. A plurality of groundelectrodes connected to the corresponding circuit blocks are-formed onthe surface of the dielectric substrate disposed opposite to the circuitsubstrate, a parasitic inductance generated in the dielectric substrateis separated for each circuit block, and wraparound of the highfrequency signal can be prevented.

[0007] In this structure, since connection of the semiconductorintegrated circuit device to the dielectric substrate, and connection ofthe dielectric substrate to the circuit substrate need to be performed,respectively, productivity is bad. Since the via-hole has a simplylinear column shape, it is necessary to draw around the high frequencysignal wiring on the semiconductor integrated circuit device and toconnect the wiring to a predetermined integrated circuit device.However, in the conventional semiconductor device, attenuation of thehigh frequency signal in the signal wiring formed in the semiconductorintegrated circuit device is remarkable.

BRIEF SUMMARY OF THE INVENTION

[0008] An object of the present invention is to provide a semiconductordevice which can enhance productivity, that is, a high frequency signaltransmission structure. Another object of the present invention is toprovide a semiconductor device which can reduce attenuation of a highfrequency signal.

[0009] According to one aspect of the present invention, there isprovided a high frequency signal transmission structure comprising: asubstrate; and a high frequency signal wiring formed on the substrate,the high frequency signal wiring including a connection portion, a padportion for external connection, and one or more dummy pad portionswhich are disposed between the connection portion and the pad portionfor external connection to restrain attenuation of a high frequencysignal.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0010]FIG. 1 is a perspective plan view of a major part of asemiconductor device according to one embodiment of the presentinvention;

[0011]FIG. 2 is a sectional view of a part taken along line II-II ofFIG. 1;

[0012]FIG. 3 is a sectional view of a part taken along line III-III ofFIG. 1;

[0013]FIG. 4 is a sectional view of a part taken along line IV-IV ofFIG. 1;

[0014]FIG. 5A is a plan view of the semiconductor device used in a firstexperiment;

[0015]FIG. 5B is a sectional view taken along N_(B)-N_(B) of FIG. 5A;

[0016]FIG. 6 is a plan view of another semiconductor device used in thefirst experiment;

[0017]FIG. 7 is a diagram showing transmission characteristics of a highfrequency signal by the first experiment;

[0018]FIG. 8 is a plan view of the semiconductor device used in a secondexperiment;

[0019]FIGS. 9A and 9B are plan views of another semiconductor deviceused in the second experiment;

[0020]FIG. 10 is a diagram showing the transmission characteristics ofthe high frequency signal by the second experiment;

[0021]FIG. 11 is a diagram showing the transmission characteristics ofthe high frequency signal by another experiment;

[0022]FIG. 12 is a perspective plan view of the major part of thesemiconductor device showing a second embodiment of the presentinvention;

[0023]FIG. 13 is a sectional view of a part taken along line XIII-XIIIof FIG. 12;

[0024]FIG. 14A is a plan view of the semiconductor device used in athird experiment;

[0025]FIG. 14B is a sectional view of a part taken along lineXN_(B)-XN_(B) of FIG. 14A;

[0026]FIG. 15 is a plan view of another semiconductor device used in thethird experiment;

[0027]FIG. 16 is a diagram showing the transmission characteristics ofthe high frequency signal by the third experiment;

[0028]FIG. 17 is a plan view of the semiconductor device used in afourth experiment;

[0029]FIG. 18 is a plan view of another semiconductor device used in thefourth experiment;

[0030]FIG. 19 is a diagram showing the transmission characteristics ofthe high frequency signal by the fourth experiment;

[0031]FIGS. 20A and 20B are plan views of the semiconductor device usedin a fifth experiment, respectively; and

[0032]FIG. 21 is a diagram showing the transmission characteristics ofthe high frequency signal by the fifth experiment.

DETAILED DESCRIPTION OF THE INVENTION FIRST EMBODIMENT

[0033]FIG. 1 is a perspective plan view of a major part of asemiconductor device according to one embodiment of the presentinvention, FIG. 2 is a sectional view of a part taken along line II-IIof FIG. 1, FIG. 3 is a sectional view of a part taken along line III-IIIof FIG. 1, and FIG. 4 is a sectional view of a part taken along lineIV-IV of FIG. 1. This semiconductor device is called a chip size package(CSP), includes, for example, a transmitted/received signal circuit ofBluetooth, and is incorporated in electronic apparatuses such as acellular phone.

[0034] The semiconductor device includes a semiconductor substrate 1which has a planar square shape and which is formed of Si or GaAs. In anupper surface peripheral portion of the semiconductor substrate 1, aplurality of connection pads 2 formed of aluminum are electricallyconnected to and disposed in an integrated circuit or circuits (notshown) including one or more transmitted/received signal circuitsdisposed in an upper surface middle part of the semiconductor substrate1. An insulating film 3 formed of inorganic insulating materials such assilicon oxide and a protective film (insulating film) 4 formed oforganic resins such as polyimide are successively stacked and disposedon the upper surfaces of the connection pads 2 and semiconductorsubstrate 1 excluding the middle parts of the respective connection pads2. The middle parts of the connection pads 2 are exposed via openings 5formed in the insulating film 3 and protective film 4.

[0035] A ground layer 6 is disposed under the protective film 4 on theupper surface middle part of the insulating film 3. The ground layer 6is constituted of an underlying metal layer 6A of copper, and an uppermetal layer 6B disposed on the underlying metal layer 6A and formed ofcopper. The layer 6 is formed substantially all over the inside of aregion in which the connection pads 2 are formed, excluding a partialregion described later as shown in FIG. 1. First to third wirings 7, 8,9 are disposed over to predetermined positions of the upper surface ofthe protective film 4 from the upper surfaces of the connection pads 2exposed via the openings 5. The first to third wirings 7, 8, 9 are alsoconstituted of underlying metal layers 7A, 8A, 9A of copper and uppermetal layers 7B, 8B, 9B disposed on the underlying metal layers 7A, 8A,9A and formed of copper. The first to third wirings 7, 8, 9 aresimultaneously formed by plating.

[0036] The first wiring (high frequency signal wiring) 7 is atransmission/reception signal line connected to a high frequencyprocessing circuit incorporated in Bluetooth. The wiring 7 isconstituted of: a square connection portion 7 a formed of a portionconnected to the connection pad 2; a circular dummy pad portion 7 b; aleading line 7 c connecting the connection portion 7 a to the dummy padportion 7 b; a circular pad portion for external connection 7 d; and aleading line 7 e connection both the pad portions 7 b, 7 d. In thiscase, only one first wiring 7 is shown as the transmission/receptionsignal line, but a transmission signal line may be formed separatelyfrom a reception signal line.

[0037] The second wiring 8 is a ground line, and is constituted of: asquare connection portion 8 a formed of the portion connected to theconnection pad 2; a circular pad portion for external connection 8 b;and a leading line 8 c connecting the connection portion 8 a to the padportion for external connection 8 b. The third wiring 9 is a wiring forcircuit other than a transmission/reception wiring, and is constitutedof: a square connection portion 9 a formed of the portion connected tothe connection pad 2; a circular tip-end pad portion 9 b; and a leadingline 9 c connecting the connection portion 9 a to the pad for externalconnection 9 b. Here, as shown in FIG. 1, the second wirings 8 which areground lines are disposed on opposite sides of the first wiring 7 whichis the transmission/reception signal line and along the first wiring 7.

[0038] A post for external connection S₀ formed of copper and having acolumnar shape is disposed on the upper surface of the pad portion forexternal connection 7 d of the first wiring 7. A dummy post D formed ofcopper is disposed on the upper surface of the dummy pad portion 7 b ofthe first wiring 7. Ground posts for external connection G formed ofcopper and having the columnar shape are respectively disposed in thepad portions for external connections 8 b of the second wirings 8. Postsfor external connection S₁ formed of copper and having the columnarshape are disposed on the upper surface of the pads for externalconnection 9 b of the third wirings 9.

[0039] All the posts S₀, S₁, G, D are disposed above the ground layer 6as shown in FIG. 1, are simultaneously formed by plating, and havesubstantially the same height. The dummy post D may have the samediameter as that of the other posts S₀, S₁, G, or a different diameter.

[0040] As shown in FIG. 2, openings 11, 12 having substantially the samesizes as those of the pad portions 7 b, 7 d are formed in the portionsof the ground layer 6 under the dummy pad portion 7 b and pad portionfor external connection 7 d of the first wiring 7. As shown in FIG. 3,the pad portion 8b under the ground post G is connected to the groundlayer 6 via an opening 13 formed in the protective film 4. As shown inFIGS. 1 and 3, the ground posts G disposed in the middle parts areelectrically connected to the ground layer 6 via the insular padportions 8 b, and the ground layer 6 are connected to the connectionpads 2 via the leading lines 8 c.

[0041] A sealing film 14 formed of organic resins such as an epoxy-basedresin is disposed on the upper surface of the protective film 4 and thefirst to third wirings 7, 8, 9 excluding all the posts S₀, S₁, G, D insuch a manner that the upper surface of the sealing film constitutessubstantially the same plane as that of the upper surfaces of all theposts S₀, S₁, G, D.

[0042] Here, in the present invention, terms “the dummy pad portion” and“the dummy post” are defined as a pad portion and post which arepositioned in terminal ends of a circuit in the form of an equivalentcircuit and which are not connected to another circuit. Functions of thedummy pad portion 7 b and dummy post D will be described later.

[0043] As described above, in this semiconductor device, the groundlayer 6 is disposed above the semiconductor substrate 1, and the firstto third wirings 7, 8, 9 including the high frequency signal wiring fortransmitting the high frequency signal are disposed on the ground layer6 via the protective film 4. Therefore, the first to third wirings 7, 8,9 including the high frequency signal wiring and the ground layer 6 maybe disposed only on the upper surface of the semiconductor substrate 1.Additionally, a dielectric substrate separate from the semiconductorsubstrate does not have to be used, and therefore a manufacturingprocess can be simplified to enhance productivity.

[0044] Moreover, when the posts S₀, S₁, G disposed on the tip-end padportions 7 d, 8 b (including the insular pad portion 8 b shown in FIG.3), 9 b of the first to third wirings 7, 8, 9 are bonded to an externalcircuit substrate (not shown), solder balls can be formed on therespective posts S₀, S₁, G to collectively bond the posts, and a step ofbonding the posts to another circuit substrate is also efficient. Inthis case, to manufacture the semiconductor device of the presentinvention, a wafer level package process can be applied. That is, it isalso possible to use a manufacturing method in which the ground layer 6,protective film 4, wirings 7, 8, 9, posts S₀, S₁, G, D, and sealing film14 are successively formed on the semiconductor wafer on which theconnection pads 2 connected to the integrated circuit and the insulatingfilm 3 exposing the middle parts of the connection pads 2 are formed,and the solder balls are formed on the respective posts S₀, S₁, G, D.Thereafter, dicing is performed to obtain individual semiconductordevices.

[0045] Next, the functions of the dummy pad portion 7 b and dummy post Dwill be described together with experiment results. First, thesemiconductor device shown in FIGS. 5A, 5B are prepared for a firstexperiment. This semiconductor device includes a semiconductor substrate21 which has a planar square shape. On the upper surface of thesemiconductor substrate 21, an insulating film 22 formed of inorganicmaterials such as silicon oxide, a ground layer 23 formed of aluminum,and a protective film 24 formed of organic resins such as polyimide aresuccessively stacked and disposed.

[0046] A wiring 25 formed of copper is disposed to extend in alongitudinal direction in the middle part of the upper surface of theprotective film 24 in a vertical direction in FIG. 5A. A circular dummypad portion 26 is disposed in the middle part of the wiring 25.Connection terminals 27, 28 having square shapes are disposed on theopposite ends of the wiring 25. A dummy post 29 formed of copper andhaving the columnar shape is disposed on the upper surface of the dummypad portion 26.

[0047] Connection terminals 30 formed of copper and having rectangularshapes are disposed in parallel with the wiring 25 on the opposite sidesof the vertical direction of the connection terminals 27, 28 in theupper surface of the protective film 24. These connection terminals 30are electrically connected to the ground layer 23 via circular openings31 formed in the protective film 24.

[0048] Here, the wiring 25 corresponds to the first wiring 7 shown inFIG. 1. The dummy pad portion 26 corresponds to the dummy pad portion 7b shown in FIG. 1. The dummy post 29 corresponds to the dummy post Dshown in FIG. 1. The ground layer 23 corresponds to the ground layer 6shown in FIG. 1.

[0049] Next, one example of a dimension of the semiconductor deviceconstituted as described above will be described. A plane size of thesemiconductor substrate 21 is 2400×2400 μm, and a thickness is 600 μm.The thickness of the insulating film 22 is 0.5 μm. The thickness of theground layer 23 is 1 μm. The thickness of the protective film 24 is 6μm. The thickness of the wiring 25 including the connection terminals27, 28 and dummy pad portion 26 is 5 μm. A width of the wiring 25 is 10μm. A length of the wiring 25 including the dummy pad portion 26 is 1800μm.

[0050] Each plane size of the connection terminals 27, 28 is 170×170 μm.A diameter of the dummy pad portion 26 and dummy post 29 is 300 μm. Aheight of the dummy post 29 is 100 μm. Each plane size of the connectionterminals 30 is 340×170 μm. An interval between the respectiveconnection terminals 30 and the corresponding connection terminals 27,28 is 130 μm. The diameter of the opening 31 is 130 μm.

[0051] Next, measuring instruments such as a network analyzer were usedto check transmission characteristics S₂₁ of the high frequency signalof the semiconductor device constituted as described above. In thiscase, a probe for measurement was brought in contact with the connectionterminals 27, 28, 30. Moreover, for the semiconductor device of thepresent invention, a device including the dummy post 29 on the dummy padportion 26 (hereinafter referred to as the CSP including the post), anda device which included the dummy pad portion 26 but the dummy post 29was not formed on the portion (hereinafter referred to as the CSPwithout the post) were prepared. For comparison, as shown in FIG. 6, asemiconductor device which did not include the dummy post 29 and dummypad portion 26 and which included only the wiring 25 was prepared(hereinafter referred to as the CSP including only the wiring).

[0052] Moreover, when the transmission characteristics S₂₁ of the highfrequency signal of each CSP were measured, the results shown in FIG. 7were obtained. In FIG. 7, a solid line indicates the transmissioncharacteristics S₂₁ of the CSP including the post (or with the pad), anda one-dot chain line indicates the transmission characteristics S₂₁ ofthe CSP including only the wiring (or without the pad). In this case,the transmission characteristics S₂₁ of the CSP without the post aresubstantially the same as the transmission characteristics S₂₁ of theCSP including the post shown by the solid line, and are therefore shownby the solid line.

[0053] As apparent from FIG. 7, up to about 19 GHz, an attenuation ofthe high frequency signal of the CSP including only the wiring, shown bythe one-dot chain line, is smaller than that of the CSP including thepost and the CSP without the post, shown by the solid line. However,with a frequency exceeding about 19 GHz, this is reversed, and theattenuations of the CSP including the post and the CSP without the post,shown by the solid line, are smaller than that of the CSP including onlythe wiring, shown by the one-dot chain line.

[0054] Therefore, in a frequency band of about 19 GHz or more, theattenuation of the high frequency signal in the CSP including the postand the CSP without the post can be restrained as compared with that ofthe CSP including only the wiring. Since the transmissioncharacteristics S₂₁ of the CSP including the post are substantially thesame as those of the CSP without the post, a difference by thepresence/absence of the post 29 is hardly seen.

[0055] Here, in FIG. 5A, it is assumed that a characteristic impedanceof the portions of the wiring 25 on the left side of the dummy padportion 26, and connection terminal 27 (i.e., the wiring 7 c andconnection portion 7 a under the dummy pad portion 7 b in FIG. 1) is Z₁,and the characteristic impedance of the dummy pad portion 26 and theportion of the dummy post 29 (i.e., the dummy pad portion 7 b and dummypost D in FIG. 1) is Z₂. It is also assumed that the characteristicimpedance of the portion of the wiring 25 on the left side of the dummypad portion 26, and the connection terminal 28 (i.e., the wiring 7 e,pad portion for external connection 7 d, and post for externalconnection So above the dummy pad portion 7 b in FIG. 1) is Z₃. Then,Z₁≈Z₂≈Z₃ is preferable in order to improve the transmissioncharacteristics.

[0056] In the above-described first experiment, the wiring 25 is assumedas a straight line. Next, as a second experiment, the wiring including abent portion will be described. In this case, the semiconductor deviceshown in FIG. 8 was prepared. In the semiconductor device shown in FIG.8, the portions having the same names as those of the semiconductordevice shown in FIG. 5A are denoted with the same reference numerals anddescribed. A sectional shape of this semiconductor device is basicallythe same as that shown in FIG. 5B. However, in this case, only the dummypad portion 26 is provided, and the dummy post is not disposed on theportion.

[0057] In this semiconductor device, the wiring 25 is bent and extendedso as to change a direction substantially by 90° in the middle part, andthe circular dummy pad portion 26 is disposed in the bent portion. Inthis case, a center of the dummy pad portion 26 corresponds to that ofthe semiconductor substrate 21, and is disposed in a bent point or acenter point of the bent portion of the wiring 25.

[0058] Next, the transmission characteristics S₂₁ of the high frequencysignal of the semiconductor device constituted as described above werechecked using the measuring instruments such as the network analyzer. Inthis case, for the comparison, the semiconductor devices shown in FIGS.9A, 9B were prepared. In the semiconductor device shown in FIG. 9A, thedummy pad portion 26 is disposed inside the bent portion of the wiring25, and in the semiconductor device shown in FIG. 9B, the dummy padportion 26 is disposed outside the bent portion of the wiring 25.

[0059] Here, a point at which two line segments of one high frequencysignal wiring intersect with each other is assumed as a bent point. Whenthe center of the dummy pad is positioned on the side having a smallintersection angle of two line segments centering on the bent point, itis assumed that the pad is positioned inside the bent portion. When thecenter is positioned on the side having a large intersection angle oftwo line segments centering on the bent point, it is assumed that thepad is positioned outside the bent portion.

[0060] Next, when the transmission characteristics S₂₁ of the highfrequency signals of the semiconductor devices shown in FIGS. 8 and 9A,9B were measured, the results shown in FIG. 10 were obtained. In FIG.10, the solid line shows the transmission characteristics S₂₁ of thesemiconductor device (hereinafter referred to as the inside-pad CSP)shown in FIG. 9A, a dotted line shows the transmission characteristicsS₂₁ of the semiconductor device (hereinafter referred to as thecenter-pad CSP) shown in FIG. 8, and the one-dot chain line shows thetransmission characteristics S₂₁ of the semiconductor device(hereinafter referred to as the outside-pad CSP) shown in FIG. 9B.

[0061] As apparent from FIG. 10, the high frequency signal issubstantially similarly attenuated for each CSP up to about 6 GHz.However, in a range of about 6 GHz to 19 GHz, the attenuation of thehigh frequency signal of the inside-pad CSP shown by the solid line islargest. Next, the attenuation of the high frequency signal of thecenter-pad CSP shown by the dotted line is large, and the attenuation ofthe high frequency signal of the outside-pad CSP shown by the one-dotchain line is smallest. When the high frequency signal exceeds about 19GHz, the attenuation of the high frequency signal of the inside-pad CSPshown by the solid line is smallest, and next the attenuation of thehigh frequency signal of the center-pad CSP shown by the dotted line issmall, but the attenuation of the high frequency signal of theoutside-pad CSP shown by the one-dot chain line rapidly increases. Thatis, the state or amount of the attenuation of the high frequency signalof about 6 GHz to 19 GHz is completely reverse to that of the highfrequency signal exceeding about 19 GHz. Therefore, it is preferablyappropriately selected by the frequency of the high frequency signaltransmitted to the wiring 25 whether to dispose the dummy pad portion 26in a point constituting the bent portion of the wiring 25, inside thebent portion of the wiring 25, or outside the bent portion of the wiring25. Supposing that the frequency of the transmitted high frequencysignal is smaller than about 19 GHz, or exceeds about 19 GHz, the bentportion is most preferably positioned in the pad center as shown by thedotted line.

[0062] Next, the function of the opening 11 of the ground layer 6 underthe dummy pad portion 7 b shown in FIG. 2 will be described togetherwith the experiment result. First, the semiconductor devicesubstantially similar to that shown in FIGS. 5A, 5B was prepared.Additionally, in this case, the diameters of the dummy pad portion 26and dummy post 29 were set to 150 μm, and the other dimensions were setin the same manner as in the above-described case.

[0063] Moreover, the followings were prepared: a first semiconductordevice in which an opening having a diameter of 150 μm (the same as thediameter of the dummy pad portion 26) was formed in the ground layer 23under the dummy pad portion 26; a second semiconductor device in whichthe opening having a diameter of 170 μm was formed; a thirdsemiconductor device in which the opening having a diameter of 190 μmwas formed; a fourth semiconductor device in which the opening having adiameter of 130 μm was formed; and a fifth semiconductor device in whichthe opening was not formed. As described above, for the respectivesemiconductor devices, the device in which the dummy post 29 was notdisposed on the dummy pad portion 26, and the device in which the dummypost 29 was disposed were prepared.

[0064] Moreover, when the transmission characteristics S₂₁ of the highfrequency signals of the first to fifth semiconductor devices weremeasured, the results shown in FIG. 11 were obtained. That is, in thefirst to third semiconductor devices, substantially the sametransmission characteristics S₂₁ were obtained as shown by the solidline in FIG. 11. In the fourth and fifth semiconductor devices,substantially the same transmission characteristics S₂₁ were obtained asshown by the dotted line in FIG. 11. Moreover, the device in which thedummy post 29 was not disposed on the dummy pad portion 26 and thedevice in which the dummy post 29 was disposed indicated substantiallythe same transmission characteristics S₂₁. Therefore, in FIG. 11, thesame characteristic curves are shown.

[0065] As apparent from FIG. 11, the attenuations of the high frequencysignals of the first to third semiconductor devices shown by the solidline are smaller than those of the fourth and fifth semiconductordevices shown by the dotted line in a frequency band of about 26 GHz toabout 42 GHz. However, this relation is reversed in another frequencyband, that is, in the frequency band smaller than about 26 GHz and thatlarger than about 42 GHz. The attenuations of the fourth and fifthsemiconductor devices shown by the dotted line are smaller than those ofthe first to third semiconductor devices shown by the solid line. In thefrequency band smaller than about 26 GHz, the attenuations of the firstto third semiconductor devices shown by the solid line are larger thanthose of the fourth and fifth semiconductor devices shown by the dottedline, but a difference between the both is not very large.

[0066] In the above-described experiment, one example was simply usedwith respect to the size of the dummy pad portion 26, the thickness ofthe protective film 24, and the like. Therefore, when each parameter ischanged, a correlation between the size of the opening of the groundlayer 23 and an attenuation ratio of the frequency band is presumed tochange. Here, what is important is that the size of the opening formedin the ground layer 23 under the dummy pad portion 26 can be selected toobtain optimum transmission characteristics S₂₁ with respect to thefrequency transmitted to the wiring.

[0067] In consideration of the above, since the circular dummy padportion 7 b broader than the first wiring 7 is disposed midway in thefirst wiring 7 in order to reduce the attenuation of the high frequencysignal as described above, the shape of the whole first wiring 7including the dummy pad portion 7 b largely differs in the portionconstituting the dummy pad portion 7 b.

[0068] As a result, when the opening 11 is not disposed in the groundlayer 6, a floating capacity in the portion constituting the dummy padportion 7 b increases, the characteristic impedance largely changes, andthe transmission characteristics drop. Then, when the opening 11 havinga diameter substantially the same as or larger than that of the dummypad portion 7 b is formed in the ground layer 6 under the dummy padportion 7 b, the floating capacity in the portion constituting dummy padportion 7 b decreases, the change of the characteristic impedance isreduced, and the transmission characteristics can be enhanced.

[0069] The opening 12 of the ground layer 6 under the pad portion forexternal connection 7 d shown in FIG. 2 is also disposed for the similarreason. As shown in FIG. 8 and FIGS. 9A and 9B, this also applies to thecase in which the wiring includes the bent portion.

[0070] In FIG. 11, the solid line and dotted line have a relation suchthat the lines mutually shift in a left and right direction. From thisrespect, it can be said that when the diameters of the openings 11, 12of the ground layer 6 are changed in accordance with the frequency, itcan be said to be possible to shift a satisfactory range of thetransmission characteristics S₂₁.

[0071] In the first embodiment, the ground layer 6 is disposed under thewirings 7, 8, 9. However, the ground layer can be formed on theprotective film in the same manner as the wiring as hereinafterdescribed as a second embodiment.

SECOND EMBODIMENT

[0072]FIG. 12 is a perspective plan view of the major part of thesemiconductor device as one embodiment of the present invention, andFIG. 13 is a sectional view of a part taken along line XIII-XIII of FIG.12. The second embodiment is different from FIGS. 1 and 2 in that aground layer 60 is not formed between the first wiring 7, third wiring9, and the semiconductor substrate 1, and is similarly formed on theprotective film 4 in the same manner as the first wiring 7 and thirdwiring 9. The ground layer 60 is formed in a U-shaped patternsurrounding three sides excluding one side on the side of the connectionpad 2 of the first wiring 7, and is connected to the connection pads 2disposed adjacent to the connection pad 2 connected to the first wiring7. Therefore, the same materials as those of the first wiring 7 andthird wiring 9 can be used to pattern/form the ground layer 60 in thesame process as that of the first wiring 7 and third wiring 9, andproductivity is efficient. Alternately, the ground layer 60 may also beformed so as to surround the whole periphery of the first wiring 7 asthe need arises.

[0073] In the above description, the first wiring 7 which is a wiringfor the high frequency signal includes the dummy pad portion 7 b and thepad portion 7 d for external connection. The dummy post D is formed onthe dummy pad portion 7 b, and the post for external connection S₀ isformed on the pad portion 7 d for external connection. Only one firstwiring 7 is shown as the transmission/reception signal line, but thetransmission signal line may also be disposed separately from thereception signal line. In this case, the first wiring 7 is disposed in aregion surrounded by the ground layer 60.

[0074] Since the other constitution is the same as that of the firstembodiment, the description is omitted.

[0075] Next, the functions of the dummy pad portion 6 b and dummy post10 will be described together with the experiment results. First, forthe first experiment, the semiconductor devices shown in FIGS. 14A, 14Bwere prepared. The semiconductor device includes the semiconductorsubstrate 21 having the plane square shape. The oxide film 22 formed ofthe insulating materials such as silicon oxide and the protective film24 formed of the organic resins such as polyimide are disposed on theupper surface of the semiconductor substrate 21 in this order.

[0076] The wiring 25 formed of copper is disposed to extend in thelongitudinal direction in the middle part of the upper surface of theprotective film 24 in the vertical direction in FIG. 14A. In this case,the circular dummy pad portion 26 is disposed in the middle part of thewiring 25. The connection terminals 27, 28 having the square shapes aredisposed on the opposite ends of the wiring 25. The dummy post 29 formedof copper and having the columnar shape is disposed on the upper surfaceof the dummy pad portion 26.

[0077] Ground layers 41, 42 formed of copper are disposed along and inparallel with the wiring 25 on the opposite sides of a width directionof the wiring 25 on the upper surface of the protective film 24.Projections 41 a, 42 a each forming a part of the connection terminalare disposed to face the connection terminals 27, 28 in the oppositeends of the ground layers 41, 42.

[0078] Here, the wiring 25 corresponds to the first wiring 7 shown inFIG. 12. The dummy pad portion 26 corresponds to the dummy pad portion 7b shown in FIG. 12. The dummy post 29 corresponds to the dummy post Dshown in FIG. 12. The ground layers 41, 42 correspond to the thirdwiring 9 shown in FIG. 12.

[0079] Next, one example of the dimensions of the semiconductor deviceconstituted as described above will be described. The plane size of thesemiconductor substrate 21 is 2400×2400 μm, and the thickness is 600 μm.The thickness of the oxide film 22 is 0.5 μm. The thickness of theprotective film 24 is 6 μm. The thickness of the wiring 25 including theconnection terminals 27, 28 and dummy pad portion 26 is 5 μm. The widthof the wiring 25 is 10 μm. The length of the wiring 25 including thedummy pad portion 26 is 1800 μm. The plane sizes of the connectionterminals 27, 28 are each 170×170 μm. The diameters of the dummy padportion 26 and dummy post 29 are each 300 μm. The height of the dummypost 29 is 100 μm.

[0080] The lengths of the ground layers 41, 42 are each 2140 μm. Thelength of the portion excluding the projections 41 a, 42 a of the groundlayers 41, 42 is 1800 μm. Therefore, the length of the projections 41 a,42 a is 170 μm which is the same as that of one side of the oppositeconnection terminals 27, 28. The width of the portion including theprojections 41 a, 42 a of the ground layers 41, 42 is 340 μm. Aninterval between the projections 41 a, 42 a and the connection terminals27, 28 is 130 μm.

[0081] Next, the measuring instruments such as the network analyzer wereused to check the transmission characteristics S₂₁ of the high frequencysignal of the semiconductor device constituted as described above. Inthis case, the probe for measurement was brought in contact with theportions constituting the connection terminals 27, 28 and projections 41a, 42 a. Moreover, for the semiconductor device of the presentinvention, the device including the dummy post 29 on the dummy padportion 26 (hereinafter referred to as the CSP including the post), andthe device which included the dummy pad portion 26 but in which thedummy post 29 was not formed on the portion (hereinafter referred to asthe CSP without the post) were prepared. For comparison, as shown inFIG. 15, the semiconductor device which did not include the dummy post29 and dummy pad portion 26 and which included only the wiring 25 wasprepared (hereinafter referred to as the CSP including only the wiring).

[0082] Moreover, when the transmission characteristics S₂₁ of the highfrequency signal of each CSP were measured, the results shown in FIG. 16were obtained. In FIG. 16, the solid line indicates the transmissioncharacteristics S₂₁ of the CSP including the post, the dotted lineindicates the transmission characteristics S₂₁ of the CSP without thepost, and the one-dot chain line indicates the transmissioncharacteristics S₂₁ of the CSP including only the wiring or no pad.

[0083] As apparent from FIG. 16, up to about 5 GHz, the attenuation ofthe high frequency signal of the CSP including only the wiring (withoutthe pad), shown by the one-dot chain line, is smaller than that of theCSP including the post, shown by the solid line, and the CSP without thepost, shown by the dotted line. However, with the frequency exceedingabout 5 GHz, this is reversed, and the attenuations of the CSP includingthe post, shown by the solid line, and the CSP without the post, shownby the dotted line, are smaller than that of the CSP without the pad,shown by the one-dot chain line. Therefore, in the frequency band ofabout 5 GHz or more, the attenuation of the high frequency signals ofthe CSP including the post and the CSP without the post can be reducedas compared with the CSP without the pad.

[0084] Next, seen from the CSP including the post shown by the solidline and the CSP without the post shown by the dotted line, theattenuation of the high frequency signal of the CSP including the postshown by the solid line is slightly smaller than that of the CSP withoutthe post shown by the dotted line in the frequency band of about 5 GHzto about 25 GHz, Therefore, in the frequency band of about 5 GHz toabout 25 GHz, the attenuation of the high frequency signal of the CSPincluding the post can slightly be suppressed as compared with the CSPwithout the post.

[0085] In the above-described third experiment, the wiring 25 is assumedas the straight line. Next, as a fourth experiment, the wiring includingthe bent portion will be described. In this case, the semiconductordevice shown in FIG. 17 was prepared. In the semiconductor device shownin FIG. 17, the portions having the same names as those of thesemiconductor device shown in FIG. 12 are denoted with the samereference numerals and described. It is to be noted that the sectionalshape of this semiconductor device is basically the same as that shownin FIG. 13.

[0086] In this semiconductor device, the wiring 25 is bent substantiallyby 90° in the middle part or center point, and the circular dummy padportion 26 is positioned in the portion constituting the bent portion ofthe wiring 25. In this case, the center of the dummy pad portion 26corresponds to that of the semiconductor substrate 21, and is disposedin the center point of the bent portion of the wiring 25. Therefore, thecenter of the columnar dummy post 29 disposed on the dummy pad portion26 is also disposed in the point constituting the bent portion. Twoground layers 43, 44 are disposed to surround the wiring 25, and areentirely disposed in a substantially square frame shape.

[0087] Next, one example of the dimensions of the semiconductor deviceconstituted as described above will be described. The plane size of thesemiconductor substrate 21 is 2400×2400 μm. The width of the wiring 25is 10 μm. The plane size of the connection terminals 27, 28 is 170×170μm. The diameters of the dummy pad portion 26 and dummy post 29 are each300 μm. The height of the dummy post 29 is 100 μm.

[0088] The widths of the ground layers 43, 44 are the same as the lengthof one side of the connection terminals 27, 28 which is 170 μm. On theother hand, that is, the length of one side of the left upper groundlayer 43 of FIG. 17 is 855 μm. The length of a long side of the otherground layer 44 is 1755 μm, and the length of a short side is 470 μm.The interval between the ground layers 43, 44 and the connectionterminals 27, 28 is 130 μm. The length of each wiring 25 excluding theconnection terminals 27, 28 is 895 μm to the center of the circulardummy pad portion 26 formed in the position constituting the bentportion.

[0089] Next, the transmission characteristics S₂₁ of the high frequencysignal of the semiconductor device constituted as described above werechecked using the measuring instruments such as the network analyzer. Inthis case, for the semiconductor devices of the present invention, thedevice in which the dummy post 29 was disposed on the dummy pad portion26 (hereinafter referred to as the CSP including the post), and thedevice in which the dummy pad portion 26 was disposed but the dummy post29 was not formed on the portion (hereinafter referred to as the CSPwithout the post) were prepared. Moreover, for comparison, as shown inFIG. 18, the semiconductor device which did not include the dummy post29 and dummy pad portion 26 and which included only the wiring 25(hereinafter referred to as the CSP including only the wiring or withoutthe pad) was prepared.

[0090] In the above-described semiconductor device, when thetransmission characteristics S₂₁ of the high frequency signal of eachCSP were measured, the results shown in FIG. 19 were obtained. In FIG.19, the solid line indicates the transmission characteristics S₂₁ of theCSP including the post, the dotted line indicates the transmissioncharacteristics S₂₁ of the CSP without the post, and the one-dot chainline indicates the transmission characteristics S₂₁ of the CSP withoutthe pad.

[0091] As apparent from FIG. 19, for the attenuation of the highfrequency signal, up to about 5 GHz and at about 27 GHz or more, theattenuation of the CSP without the pad shown by the one-dot chain lineis smaller than that of the CSP including the post shown by the solidline and the CSP without the post shown by the dotted line. However, inan intermediate frequency band, this relation is reversed, and theattenuations of the CSP including the post shown by the solid line andthe CSP without the pad shown by the dotted line are smaller than theattenuation of the CSP without the pad shown by the one-dot chain line.

[0092] Therefore, in the frequency band of about 5 GHz to about 27 GHz,the attenuations of the high frequency signals of the CSP including thepost and the CSP without the post can be reduced as compared with theCSP including only the wiring. As a result, in FIG. 1, even when thewidth of the first wiring 7 as the transmission/reception signal line ofBluetooth is, for example, about 10 μm and remarkably small, theattenuation of the high frequency signal can be reduced. It is to benoted that the CSP including only the wiring is preferable in thefrequency band of about 5 GHz or less, but it is not to say that thereis a remarkable difference between the CSP including the post and theCSP without the post.

[0093] Next, seen from the CSP including the post shown by the solidline and the CSP without the post shown by the dotted line, theattenuation of the high frequency signal of the CSP including the postshown by the solid line is slightly smaller than that of the CSP withoutthe post shown by the dotted line in the frequency band of about 5 GHzto about 23 GHz. Therefore, the attenuation of the high frequency signalin the CSP including the post can slightly be reduced as compared withthe CSP without the post in the frequency band of about 5 GHz to about23 GHz.

[0094] In the above-described fourth experiment, the case in which thecenter of the dummy pad portion 26 was disposed so as to agree with thecenter point of the bent portion of the wiring 25. Next, a fifthexperiment will be described in which the dummy pad portion 26 isdisposed inside and outside of the bent portion of the wiring 25. Inthis case, the semiconductor devices shown in FIGS. 20A, 20B wereprepared. In the semiconductor device shown in FIG. 20A, the dummy padportion 26 is disposed inside the bent portion of the wiring.25. In thesemiconductor device shown in FIG. 20B, the dummy pad portion 26 isdisposed outside the bent portion of the wiring 25. In this case, onlythe dummy pad portion 26 is disposed, and the post is not disposed onthe portion. Here, the point at which two line segments of one highfrequency signal wiring intersect with each other is assumed as thecenter point of the bent portion. When the center of the dummy pad ispositioned on the side having a small intersection angle of two linesegments centering on the bent point, it is assumed that the pad ispositioned inside the bent portion. When the center is positioned on theside having a large intersection angle of two line segments centering onthe bent point, it is assumed that the pad is positioned outside thebent portion.

[0095] Next, when the transmission characteristics S₂₁ of the highfrequency signals of the semiconductor devices shown in FIGS. 20A, 20Bwere measured, the results shown in FIG. 21 were obtained. In FIG. 21,the solid line shows the transmission characteristics S₂₁ of thesemiconductor device (hereinafter referred to as the inside-pad CSP)shown in FIG. 20A, and the one-dot chain line shows the transmissioncharacteristics S₂₁ of the semiconductor device (hereinafter referred toas the outside-pad CSP) shown in FIG. 20B. In this case, the dotted lineshown in FIG. 21 shows the transmission characteristics S₂₁ of thesemiconductor device (hereinafter referred to as the center-pad CSP)which includes only the dummy pad portion 26 and in which the post isnot disposed on the portion in the case shown in FIG. 17 in the samemanner as the dotted line shown in FIG. 19.

[0096] As apparent from FIG. 21, the high frequency signal issubstantially similarly attenuated for each CSP up to about 19 GHz.However, when the frequency exceeds about 19 GHz, the attenuation of thehigh frequency signal of the inside-pad CSP shown by the solid line issubstantially constant, the attenuation of the high frequency signal ofthe outside-pad CSP shown by the one-dot chain line rapidly increases,and the attenuation of the high frequency signal of the center-pad CSPshown by the dotted line indicates intermediate properties. Therefore,the dummy pad portion 26 is more preferably disposed in the pointconstituting the bent portion of the wiring 25 or inside the bentportion of the wiring 25 rather than disposed outside the bent portionof the wiring 25.

[0097] In the above-described embodiment, only one dummy pad portion anddummy post are formed in the wiring for the high frequency signal.However, when the wiring for the high frequency signal is long, aplurality of wirings may also be disposed at a predetermined interval,for example, at an interval of about 1 mm. Moreover, a ground patternformed along the high frequency signal wiring is shaped to be integratedwith that formed in a pattern shape in each post other than the post forthe high frequency signal wiring and around the wiring for the circuitconnected to the post, and this is efficient. In the above-describedembodiments, the semiconductor device including the wiring fortransmitting the high frequency signal has been described, but thepresent invention can also be applied to the circuit substratesincluding a high frequency circuit in a device other than thesemiconductor device.

[0098] As described above, according to the present invention, theground layer is disposed on the semiconductor substrate, and the wiringincluding the high frequency signal wiring for transmitting the highfrequency signal is disposed on the ground layer via the insulatingfilm. Therefore, the wiring including the high frequency signal wiringand the ground layer may be disposed only on one surface of thesemiconductor substrate, and therefore the manufacturing process can besimplified.

[0099] Moreover, according to the present invention, the dummy padportion for reducing the attenuation of the high frequency signal isdisposed midway in the high frequency signal wiring for transmitting thehigh frequency signal. Therefore, even when the width of the highfrequency signal wiring is small, the attenuation of the high frequencysignal can be reduced.

What is claimed is:
 1. A high frequency signal transmission structurecomprising: a substrate; and a high frequency signal wiring formed onthe substrate, the high frequency signal wiring including a connectionportion, a pad portion for external connection, and one or more dummypad portions which are disposed between the connection portion and thepad portion for external connection to restrain attenuation of a highfrequency signal.
 2. The high frequency signal transmission structureaccording to claim 1, wherein the dummy pad portion of the highfrequency signal wiring is disposed between the connection portion andthe pad portion for external connection and in a position whereimpedances of the respective portions are substantially equal.
 3. Thehigh frequency signal transmission structure according to claim 1, whichfurther comprises a post for external connection formed on the padportion for external connection.
 4. The high frequency signaltransmission structure according to claim 3, which further comprises adummy post formed on the dummy pad portion.
 5. The high frequency signaltransmission structure according to claim 4, which further includes asealing film formed on the substrate excluding a portion forming a postfor external connection and a portion forming the dummy pad portion. 6.The high frequency signal transmission structure according to claim 1,wherein the substrate has a semiconductor substrate including anintegrated circuit.
 7. The high frequency signal transmission structureaccording to claim 6, wherein the semiconductor substrate includes aconnection pad connected to the integrated circuit, and the connectionportion of the high frequency signal wiring is connected to theconnection pad.
 8. The high frequency signal transmission structureaccording to claim 1, which further comprises: a ground layer and aninsulating film formed on the ground layer between the substrate and thehigh frequency signal wiring.
 9. The high frequency signal transmissionstructure according to claim 8, wherein the ground layer includes anopening having the same width as or a width larger than that of the highfrequency signal wiring in a portion corresponding to the high frequencysignal wiring.
 10. The high frequency signal transmission structureaccording to claim 8, wherein the high frequency signal wiring issubstantially linear over a total length, and a high frequency signal of19 GHz or more is transmitted to the high frequency signal wiring. 11.The high frequency signal transmission structure according to claim 8,wherein the high frequency signal wiring includes a bent portion inwhich a direction of the wiring is bent, and the dummy pad portion isformed on the bent portion.
 12. The high frequency signal transmissionstructure according to claim 8, wherein a center of the dummy padportion is positioned in a center point of the bent portion.
 13. Thehigh frequency signal transmission structure according to claim 8,wherein the dummy pad portion is formed outside the bent portion. 14.The high frequency signal transmission structure according to claim 13,wherein a high frequency signal of about 6 GHz to about 19 GHz istransmitted to the high frequency signal wiring.
 15. The high frequencysignal transmission structure according to claim 8, wherein the dummypad portion is formed inside the bent portion.
 16. The high frequencysignal transmission structure according to claim 15, wherein a highfrequency signal of 19 GHz or more is transmitted to the high frequencysignal wiring.
 17. The high frequency signal transmission structureaccording to claim 8, which further comprises a ground post connected tothe ground layer and formed on the insulating film.
 18. The highfrequency signal transmission structure according to claim 1, whereinthe ground layer surrounding at least three peripheral directions of thehigh frequency signal wiring is formed on the same plane as the highfrequency signal wiring.
 19. The high frequency signal transmissionstructure according to claim 1, wherein a high frequency signal of 5 GHzor more is transmitted to the high frequency signal wiring in a circuitsubstrate for the high frequency signal.
 20. The high frequency signaltransmission structure according to claim 19, wherein the high frequencysignal wiring is substantially linear over a total length in the circuitsubstrate for the high frequency signal.
 21. The high frequency signaltransmission structure according to claim 19, wherein the high frequencysignal wiring has a bent portion in which a direction of the wiring isbent, and the dummy pad portion is formed in the bent portion.
 22. Thehigh frequency signal transmission structure according to claim 21,wherein a center of the dummy pad portion is positioned in a centerpoint of the bent portion.
 23. The high frequency signal transmissionstructure according to claim 21, wherein the dummy pad portion is formedinside the bent portion.
 24. The high frequency signal transmissionstructure according to claim 23, wherein a high frequency signal of 19GHz or more is transmitted to the high frequency signal wiring.
 25. Ahigh frequency signal transmission structure comprising: asemiconductive substrate including an integrated circuit and aconnection pad connected to the integrated circuit; an insulating filmformed on the semiconductor substrate and including an opening in whichthe connection pad is exposed; a ground layer formed on the insulatingfilm; a protective film formed to coat the ground layer; a wiring fortransmitting a high frequency signal, which is formed on the substrateand which includes a connection portion connected to the connection pad,a pad portion for external connection, and one or more dummy padportions disposed between the connection portion and the pad portion forexternal connection to restrain attenuation of the high frequencysignal; and a post for external connection formed on the pad portion forexternal connection of the wiring.
 26. The high frequency signaltransmission structure according to claim 25, wherein the connection padis arranged in a peripheral edge of the semiconductor substrate, and theground layer is formed substantially all over the inside of a regionforming the connection pad.
 27. The high frequency signal transmissionstructure according to claim 26, wherein the ground layer includes anopening having the same width as or a width larger than that of the highfrequency signal wiring in a portion corresponding to the high frequencysignal wiring.
 28. A high frequency signal transmission structurecomprising: a semiconductor substrate including an integrated circuitand a connection pad connected to the integrated circuit; an insulatingfilm formed on the semiconductor substrate and including an opening inwhich the connection pad is exposed; a wiring for transmitting a highfrequency signal, which is formed on the protective film and which isconnected to the connection pad and which includes a connection portion,a pad portion for external connection, and one or more dummy padportions disposed between the connection portion and the pad portion forexternal connection to restrain attenuation of a high frequency signal;and a ground layer surrounding at least three peripheral directions ofthe wiring for transmitting the high frequency signal on the insulatingfilm.
 29. The high frequency signal transmission structure according toclaim 28, which further comprises a post for external connection formedon the pad portion for external connection of the wiring.
 30. The highfrequency signal transmission structure according to claim 28, whichfurther comprises a dummy post formed on the dummy pad portion.